SLID bonding for thermal interfaces - imapsfrance.org

1 slid bonding for thermal interfaces thermal performance Technology for a better society Outline Background and motivation The HTPEP project Solid-Liquid Inter-Diffusion ( slid ). Au-Sn slid . Cu-Sn slid . Reliability and bond integrity Alternative HT TIM technologies comparison Case study HT (>200 C) power controller Stationary performance Conclusions Acknowledgements Technology for a better society The HTPEP project objectives Develop a reliable packaging technology for power electronic systems operating at temperatures up to 250 C. Know-how on SiC component technology. Processes for packaging of SiC and passive components for HT application. Knowledge on failure mechanisms occurring in interconnects and materials during HT operation. Demonstrator. Technology for a better society Application Demonstrate the packaging technology in a power controller for a brushless DC motor for downhole applications. Packaging solution should enable the controller to operate for at least 6 months at an ambient temperature of 200 C and a junction temperature of 250 C.

2 Technology for a better society Die attach and thermal interface materials (TIM). Typical components Die attach: Fix components to substrate. Low thermal resistance. Electrically conductive. TIM 1: Fix substrate mechanically to a support structure. Ensure low thermal resistance. TIM 2: Low thermal resistance between support structure and external housing. TIM 2. TIM 1. Die attach Technology for a better society Substrate technology Silicon nitride, Si3N4. thermal conductivity: up to 90 W/mK. CTE: ~ ppm/K @ 250-300 C. Flexural strength: 750-900 MPa Durable and robust SiC BJT. during thermal cycling Cu conductors Technology for a better society Die attach/interconnect technology: slid . slid Solid-Liquid Inter-Diffusion Creates a bond that is stable at higher temperature than the initial process temperature Au-Sn slid : up to 500 C. Cu-Sn slid : up to 670 C. ~10 m Au-Sn slid As bonded Cu-Sn slid As bonded Technology for a better society Solid-Liquid Inter-Diffusion ( slid ).

3 Thin low Tm Before Uses a two-metal system: bonding Hi Tm Lo Tm interlayer sandwished at RT. One HT and one LT melting metal. Hi Tm between high Tm joint parts At process temp. above the lower melting point. Inter-diffusion causes IMCs to form. : Cu-Sn slid , where a During Melting of low Tm Cu Cu3Sn Cu bond is created. bonding Hi Tm interlayer and Liquid This bond is stable up to 676 C at TB. Hi Tm interdiffusion (process temp of 250-300 C). Homogeneous After Hi Tm joint / IMC. bonding formation where IMC. at TB solidification is Hi Tm isothermal Technology for a better society Au-Sn slid . Advantages: HT stability and reliability. Oxidation resistant. Relatively low processing temp. Mechanically robust. Au has three functions: bonding . Diffusion barrier. CTE mismatch absorption. Disadvantages: Novel system relatively unexplored. High cost. Okamoto. Au-sn (Gold-Tin). J. Phase Equilib. 2007. 28(5): p. 490-490. Liu. Liu. K. Ishida.

4 And Jin. Thermodynamic modeling of the Au-In-Sn system. J. Electron. 2003. 32(11): p. 1290-1296. Technology for a better society Die attach processing Bond Characterization The bond interface is a uniform Au-rich phase. identified by EDS. to be the phase (with a melting point of 522 C). 100 at% Au Au 90 at% Au10 at% Sn 90 at% Au10 at%. Sn Tollefsen et "Au-Sn slid bonding for high temperature applications". HiTEN 2011. Technology for a better society Reliability testing Die shear strength Chip Substrate Superb bond strength: >78 MPa. Unaged 500 cycles (0-200 C, 10 C/min). 1000 cycles (0-200 C, 10 C/min). Aged (6 months, 250 C). 100 Clamp Hotplate Die shear strength (MPa). 80 SiC. 60 Au . Au 40. NiP. 20 Cu MIL-STD-883H X-section 0. Tollefsen et "Au-Sn slid bonding for high temperature applications". HiTEN 2011. Technology for a better society HT TIM comparison chart Name Material base Effective thermal Degradation Outgassing Expected final Estimated thermal conductivity temperature @ 300 C layer thickness resistance (W/m K) ( C) ( m) (mm2 K/W).

5 Au-Sn slid Gold and tin 60 Tm: 522 - ~10 ~ Cu-Sn slid Copper and tin 104 Tm: 676 - <10 < Aptiv 1000 Semi-crystalline polymer 200 Low 8 32. film Aptiv 1102 Semi-crystalline polymer 200 Low 12 28. film filled with talc ( ). Duralco 4703 Epoxy with Al2O3 powder 330 ~50 ~20. Epo-tek 353ND Epoxy 412 ~4-6 ~40. Epo-tek H74 Epoxy 425 >502 >40. Epo-tek H77 Epoxy 405 % >502 >76. Resbond 906 Silicate with magnesia 1650 Low ~100 ~ Resbond 931 Silicate with graphite 8 3000 - ~100 ~ Resbond 954 Silicate with stainless >2 1200 Low ~100 ~50. Staystik 581 Silver >3 300 Low 38 Staystik 682 Aluminum nitride >1 300 Low 38 38. 1 In-plane 2 Particle size Technology for a better society Case study Power controller for a brushless DC motor for downhole applications. Motor drive key features: Half bridge topology Switching capability per phase 400 V, 5 A. May be combined for 3-phase kVA total power delivery Power card key specs: Up to 250 C. 6 month operation Technology for a better society Power card Parts Multilayer capacitors SiC Schottky diode Cu / Ni / Au SiC BJT (Back side).

6 20 mm Si3N4 Ceramic resistors 34 mm substrate Technology for a better society Power card TIM. Au-Ge solder Au-Sn slid slid or adhesive (Back side). Duralco 4703. Technology for a better society Power card Dissipation 7 mW 35 mW. 10 mW. 700 mW. 10 W. 10 W. 350 mW 900 mW. (Pwire bonds: typically 2 13 mW / bond) (Ptot 22 W). Technology for a better society Case study BC. h = 500 W/m2K. TIM: Graphite-oil h = 100 W/m2K. h = 100 W/m2K. Technology for a better society Case study Temperature distribution Technology for a better society Case Study Temperature distribution Cu-Sn slid Duraclo 4703. P = 10 W. P = 20 W. Technology for a better society Case study Temperature drop Technology for a better society Case study Temperature drop 10 W. SiC BJT. T 1 C. Die attach (Au-Sn slid ) Shell T < C T < C. Substrate T 8 C & 7 C TIM: Graphite-oil T < C Ambient Base plate T 5 C. TIM: Power card T 2-3 C. T < C & 5 C. Cu-Sn slid . Duralco 4703.

7 SiC BJT Ambient Technology for a better society Case study Temperature drop 20 W. Substrate T 15 C & 15 C. Ambient T 9 C. TIM Power card T < C & 14 C. SiC BJT Ambient Technology for a better society Case study Derating of TIM specs Technology for a better society Case study Temperature profile Technology for a better society Potential life time A small reduction in operation temperature may provide a significant improvement in reliability and lifetime of a device. M. Watts "Design Considerations for High Temperature Hybrid Manufacturability". HiTEC 2008. Technology for a better society Concluding remarks slid bonding show great TIM potential for high reliability, performance and temperature applications. Primarily due to: Low thermal resistance. Uniform joint (low "contact resistance"). HT stability and reliability Mechanically robust Further investigations of slid bonding as a TIM is needed. Applicability for larger and more irregular surfaces.

8 Technology for a better society Acknowledgements The HTPEP project and its sponsors and partners My co-authors Torleif A. Tollefsen Olav Storstr m Technology for a better society Thanks for your attention! HTPEP. Andreas Larsson SINTEF ICT. Instrumentation dept. Technology for a better society